Stabilized solvent system



United States l atent O Delaware No Drawing. Filed May 19, 1966, Ser. No. 551,200 8 Claims. (Cl. 260652.5)

This application is a continuation-in-part of S.N. 325,130 filed November 20, 1963 now abandoned.

The present invention relates to a novel and useful composition of matter. More particularly the present invention concerns the use of a class of materials in minor amounts to inhibit 1,1,l-tn'chloroethane (methyl chloroform) against metal induced deterioration, especially to inhibit that deterioration induced by the metals zinc, aluminum and iron. Further, the present invention relates to a class of materials useful to inhibit deterioration of chlorinated saturated aliphatic hydrocarbons in general.

It is now Well established that 1,1,1-trichloroethane (methyl chloroform) is a very useful industrial solvent and that it is one, if not the most, readily degradable of the chlorinated aliphatic hydrocarbons when in contact with aluminum or iron. This degradation or deterioration occurs when the solvent is cold or hot. When the solvent is stabilized with usual stabilizing agents such as nitromethane and/ or dioxane to inhibit deterioration by these two metals (i.e, aluminum and iron), it will attack zinc unless further stabilized. US. Patent No. 2,811,252 discloses the use of 1,4-dioxane and US. Patent No. 2,923,747 discloses the use of dioxane and nitromethane to prevent aluminum and iron deterioration US. Patent No. 3,049,571 discloses the use of a Vicinal epoxide in combination with nitromethane and/or dioxane to stabilize the 1,1,1-trichlorethane and thus inhibit deterioration by all three metals. While these compositions have been commercially successful, certain new uses, wherein the solvent con-1d be used if the stabilizers would carry through carbon absorption treatments, have necessitated the search for a class of materials which will inhibit or stablize against deterioration of the 1,1,1-trichloroethane, and yet remain in the solvent when said solvent is cleaned up by the carbon absorption technique.

It has now been found that a small amount of an unsaturated cyclic inner diether selected from the group consisting of 2,3-dihydro-p-dioxin (dioxene),

and, p-dioxin (dioxadiene) and mixtures thereof, as well as mixtures of either or both of said diethers with 1,4-dioxane, will stabilize 1,1,1- trichloroethane against aluminum, iron and/or zinc deterioration. Further, the stabilizers, dioxene and dioxadiene, will pass out of carbon absorption equipment with the solvent when steamed in the usual manner. While it is to be understood that as little as 0.01% by volume of one or more of the above-mentioned diether inhibitors will inhibit the deterioration of the solvent under most conditions, it is desirable, to insure an economical stabilization-life under the usual commercial conditions, to employ "ice about 2%. Further, while 15% will insure stabilization even under the most severe conditions ordinarily encountered for indefinite periods of such use, this upper limit is the economical maximum and no more than 7% by volume of inhibitor is normally necessary.

The thus-stabilized compositions of the present invention may also be complemented by the addition of dioxane as set forth above or certain well known inhibitors which have been taught to be elfective inhibitors. Such additives are, for example, the non-primary alcohols, including the acetylenic alcohols, the amines such as the tertiary alkyl amines, the alkanol amines, and the alkylene oxides (epoxides) if employed with the alcohols, dioxane or nitroethane and the like. These additives may be employed without materially affecting the effectiveness of the present inhibitor system. The addition of adjuvant stabilizers other than the dioxins is useful in systems where carbon absorption is not practiced or where they can afford to be lost and replaced after carbon absorption clean-up. Generally, however, it is desirable, both technically and economically as Well as toxicologically, to employ only the inhibitors from the class of unsaturated cyclic inner diethers herein set forth.

It is to be further understood that while reference is generally had to the stabilization of methyl chloroform, the compounds dioxene and dioxadiene will stabilize other chlorinated, aliphatic hydrocarbons, such as those having from 1 to 2 carbon atoms and from 1 to 6 chlorine atoms respectively, and having no unsaturation, viz., methylene chloride, chloroform, carbon tetrachloride, ethylene chloride, 1,1-dichloroethane, 1,1,2-trichloroethane, 1,1,2,2 tetrachloroethane, 1,1,1,2 tetrachloroethane and the like.

The following examples illustrate the present invention but are not to be construed as limiting:

Example 1 A series of glass flasks were partially filled with methyl chloroform containing only the named inhibitor as the stabilizer and strips each of iron aluminum, and zinc were suspended half in the liquid and half above the liquid so as to be in contact with the vapors generated when the liquid is heated to the boiling, as well as the hot liquid. Each flask was fitted with a reflux condenser to prevent escape of the vapors and thus to maintain a constant liquid level after equilibrium had been reached. Heating was accomplished on a hot plate. After 14 days of continuous boiling the strips were removed and examined. The results are set forth below:

In the flasks containing as the stabilizer (inhibitor) only dioxene in the amount of 5% by volume each metal strip was bright and shiny and showed no corrosion. Further, the liquid when analyzed for HCl showed only 1 p.p.m. by volume.

In a series of tests wherein 3% each of dioxane and dioxene was used as the stabilizer (inhibitor) the same results were achieved.

In another series of tests methylchloroform containing 4% dioxane as the sole stabilizer (inhibitor) the aluminum and iron showed no corrosion but the zinc was corroded.

In another series of tests wherein no inhibitor (stabilizer) was present in the methylchloroform, the aluminum and iron were severely corroded and the aluminum when scratched below the surface of the liquid violently reacted even before the flask was heated.

In a final series of tests wherein zinc metal alone was suspended in and over the liquid, the methylchloroform containing no inhibitor (stabilizer) did not attack the zinc, while the methyl chloroform containing 3% dioxane attacked the zinc.

3 Example 2 In a series of tests conducted in a manner similar to that of Example 1, methylene chloride samples containing 0, 1, 2, 3, and 4% dioxene, respectively, were refluxed with aluminum contacting both the liquid and vapor phases. At the end of 48 hours, the uninhibited sample of methylene chloride had turned orange-brown in color and contained 14 p.p.m. by volume HCl. At the end of 7 days of continuous reflux, the samples inhibited with 1, 2, 3, and 4% by volume dioxene were all clear and colorless and contained 1 ppm. HCl.

Example 3 Example 4 To illustrate the advantage of using the inhibitors of the present invention in commercial operations where solvent recovery and clean-up are essential to the economics of the process, methyl chloroform containing various inhibitors was passed through carbon beds and then steamed out of the beds. The steamed out methyl chloroform was analyzed for inhibitor content. The results are set forth below:

Inhibitor Initial Cone, Final Cone,

percent by vol. percent by vol.

Nitromethane. 3. 0. 1 Dioxane 3.0 0. 1 Dioxene 1. 93 1. 70

Example 5 In order to illustrate the relative abilities of 1,4-dioxane, dioxene and dioxadiene to stay distributed in both the liquid and vapor phases of a chlorinated saturated aliphatic hydrocarbon solvent, 96 ml. of methyl chloroform was mixed with 4 ml. of an inhibitor and the mixture was distilled on a one plate column. The results are tabulated below. The stabilizer analysis of each 10 ml. portion of the vaporized material is set down in percent by volume of that 10 ml. increment.

10 ml. Volume Percent in Overhead oi Increment Vol. ml.

Overhead Overhead 1,4'dioxane Dioxene Dioxadiene 10 1. 12 2. 04 3. 92 20 1. 48 2. 20 3. 64 30 1. 61 2. 22 3. 54 4O 1. 69 2. 53 3.65 1. 90 2. 89 3. 21 I 2. 29 2. 72 3. 92 2. 7O 3. 17 2. 95 4. 05 3. 99 2. 54 6. 81 5. 17 2. 24 bottoms 20. 49 8. 91 1. 76

I claim:

1. A saturated aliphatic chlorinated hydrocarbon solvent composition containing as the essential inhibitor against metal induced deterioration, a stabilizing amount of a member selected from the group consisting of dioxene, dioxadiene and mixtures thereof.

2. The solvent composition of claim 1 wherein said solvent is methylchloroform.

3. The solvent composition of claim 1 wherein said essential inhibitor is dioxene.

4. The solvent composition of claim 1 wherein said essential inhibitor is dioxadiene.

5. The solvent composition of claim 2 wherein said inhibitor is present in an amount of from 0.01 to 15% by volume of said total composition.

6. The solvent composition of claim 5 wherein said essential inhibitor is dioxene.

7. The solvent composition of claim 5 wherein said essential inhibitor is dioxadiene.

8. The composition of claim 1 in which contains dioxane.

References Cited UNITED STATES PATENTS 2,371,645 3/1945 Aitchison et al 260652.5 2,852,572 9/1958 Shukys et a1 260-652 2,870,094 l/1959 Cathcart 260-6525 LEON ZITVER, Primary Examiner.

M. JACOB, Assistant Examiner. 

1. A SATURATED ALIPHATIC CHLORINATED HYDROCARBON SOLVENT COMPOSITION CONTAINING AS THE ESSENTIAL INHIBITOR AGAINST METAL INDUCED DETERIORATION, A STABILIZING AMOUNT OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF DIOXENE, DIOXADIENE AND MIXTURES THEREOF. 